[PATCH v5 06/13] powerpc: Adapt elf64_apply_relocate_add for kexec_file_load.
Thiago Jung Bauermann
bauerman at linux.vnet.ibm.com
Thu Aug 11 16:08:11 PDT 2016
Extend elf64_apply_relocate_add to support relative symbols. This is
necessary because there is a difference between how the module loading
mechanism and the kexec purgatory loading code use Elf64_Sym.st_value
at relocation time: the former changes st_value to point to the absolute
memory address before relocating the module, while the latter does that
adjustment during relocation of the purgatory.
Also, add a check_symbols argument so that the kexec code can be stricter
about undefined symbols.
Finally, add relocation types used by the purgatory.
Signed-off-by: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
---
arch/powerpc/include/asm/elf_util.h | 1 +
arch/powerpc/kernel/elf_util_64.c | 84 ++++++++++++++++++++++++++++++++++++-
arch/powerpc/kernel/module_64.c | 5 ++-
3 files changed, 88 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/elf_util.h b/arch/powerpc/include/asm/elf_util.h
index a012ba03282d..3405eeabe542 100644
--- a/arch/powerpc/include/asm/elf_util.h
+++ b/arch/powerpc/include/asm/elf_util.h
@@ -67,6 +67,7 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
const char *strtab, const Elf64_Rela *rela,
unsigned int num_rela, void *syms_base,
void *loc_base, Elf64_Addr addr_base,
+ bool relative_symbols, bool check_symbols,
const char *obj_name);
#endif /* _ASM_POWERPC_ELF_UTIL_H */
diff --git a/arch/powerpc/kernel/elf_util_64.c b/arch/powerpc/kernel/elf_util_64.c
index 8e5d400ac9f2..80f209a42abd 100644
--- a/arch/powerpc/kernel/elf_util_64.c
+++ b/arch/powerpc/kernel/elf_util_64.c
@@ -74,6 +74,8 @@ static void squash_toc_save_inst(const char *name, unsigned long addr) { }
* @syms_base: Contents of the associated symbol table.
* @loc_base: Contents of the section to which relocations apply.
* @addr_base: The address where the section will be loaded in memory.
+ * @relative_symbols: Are the symbols' st_value members relative?
+ * @check_symbols: Fail if an unexpected symbol is found?
* @obj_name: The name of the ELF binary, for information messages.
*
* Applies RELA relocations to an ELF file already at its final location
@@ -84,11 +86,13 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
const char *strtab, const Elf64_Rela *rela,
unsigned int num_rela, void *syms_base,
void *loc_base, Elf64_Addr addr_base,
+ bool relative_symbols, bool check_symbols,
const char *obj_name)
{
unsigned int i;
unsigned long *location;
unsigned long address;
+ unsigned long sec_base;
unsigned long value;
const char *name;
Elf64_Sym *sym;
@@ -121,8 +125,36 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
name, (unsigned long)sym->st_value,
(long)rela[i].r_addend);
+ if (check_symbols) {
+ /*
+ * TOC symbols appear as undefined but should be
+ * resolved as well, so allow them to be processed.
+ */
+ if (sym->st_shndx == SHN_UNDEF &&
+ strcmp(name, ".TOC.") != 0) {
+ pr_err("Undefined symbol: %s\n", name);
+ return -ENOEXEC;
+ } else if (sym->st_shndx == SHN_COMMON) {
+ pr_err("Symbol '%s' in common section.\n", name);
+ return -ENOEXEC;
+ }
+ }
+
+ if (relative_symbols && sym->st_shndx != SHN_ABS) {
+ if (sym->st_shndx >= elf_info->ehdr->e_shnum) {
+ pr_err("Invalid section %d for symbol %s\n",
+ sym->st_shndx, name);
+ return -ENOEXEC;
+ } else {
+ struct elf_shdr *sechdrs = elf_info->sechdrs;
+
+ sec_base = sechdrs[sym->st_shndx].sh_addr;
+ }
+ } else
+ sec_base = 0;
+
/* `Everything is relative'. */
- value = sym->st_value + rela[i].r_addend;
+ value = sym->st_value + sec_base + rela[i].r_addend;
switch (ELF64_R_TYPE(rela[i].r_info)) {
case R_PPC64_ADDR32:
@@ -135,6 +167,10 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
*(unsigned long *)location = value;
break;
+ case R_PPC64_REL32:
+ *(uint32_t *)location = value - (uint32_t)(uint64_t)location;
+ break;
+
case R_PPC64_TOC:
*(unsigned long *)location = my_r2(elf_info);
break;
@@ -186,6 +222,14 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
| (value & 0xfffc);
break;
+ case R_PPC64_TOC16_HI:
+ /* Subtract TOC pointer */
+ value -= my_r2(elf_info);
+ value = value >> 16;
+ *((uint16_t *) location)
+ = (*((uint16_t *) location) & ~0xffff)
+ | (value & 0xffff);
+
case R_PPC64_TOC16_HA:
/* Subtract TOC pointer */
value -= my_r2(elf_info);
@@ -195,6 +239,21 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
| (value & 0xffff);
break;
+ case R_PPC64_REL14:
+ /* Convert value to relative */
+ value -= address;
+ if (value + 0x8000 > 0xffff || (value & 3) != 0) {
+ pr_err("%s: REL14 %li out of range!\n", obj_name,
+ (long int)value);
+ return -ENOEXEC;
+ }
+
+ /* Only replace bits 2 through 16 */
+ *(uint32_t *)location
+ = (*(uint32_t *)location & ~0xfffc)
+ | (value & 0xfffc);
+ break;
+
case R_PPC_REL24:
/* FIXME: Handle weak symbols here --RR */
if (sym->st_shndx == SHN_UNDEF) {
@@ -263,6 +322,29 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
((uint32_t *)location)[1] = 0x38420000 + PPC_LO(value);
break;
+ case R_PPC64_ADDR16_LO:
+ *(uint16_t *)location = value & 0xffff;
+ break;
+
+ case R_PPC64_ADDR16_HI:
+ *(uint16_t *)location = (value >> 16) & 0xffff;
+ break;
+
+ case R_PPC64_ADDR16_HA:
+ *(uint16_t *)location = (((value + 0x8000) >> 16) &
+ 0xffff);
+ break;
+
+ case R_PPC64_ADDR16_HIGHER:
+ *(uint16_t *)location = (((uint64_t)value >> 32) &
+ 0xffff);
+ break;
+
+ case R_PPC64_ADDR16_HIGHEST:
+ *(uint16_t *)location = (((uint64_t)value >> 48) &
+ 0xffff);
+ break;
+
case R_PPC64_REL16_HA:
/* Subtract location pointer */
value -= address;
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 590e2413974f..10745ac6b004 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -443,6 +443,9 @@ int restore_r2(u32 *instruction, const char *obj_name)
* When this function is called, the module is already at its final location in
* memory, so Elf64_Shdr.sh_addr can be used for accessing the section
* contents as well as the base address for relocations.
+ *
+ * Also, simplify_symbols already changed all symbols' st_value members
+ * to absolute addresses.
*/
int apply_relocate_add(Elf64_Shdr *sechdrs,
const char *strtab,
@@ -472,7 +475,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
return elf64_apply_relocate_add(&me->arch.elf_info, strtab, rela,
num_rela, syms_base, (void *) addr_base,
- addr_base, me->name);
+ addr_base, false, false, me->name);
}
#ifdef CONFIG_DYNAMIC_FTRACE
--
1.9.1
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